Ab Initio Study of the C–O Bond Dissociation in CO₂ Reduction by Redox and Carboxyl Routes on 3d Transition Metal Systems

Abstract

The C−O bond dissociation of the CO 2 molecule via the reverse water gas shift reaction is crucial for several reactions used as renewable alternatives for fuel synthesis. However, our atomistic understanding of this process on transition metal (TM) clusters, where quantum-size effects might play a significant role, is far from complete. Here, we addressed the C−O bond dissociation by redox and carboxyl routes on 13-atom TM (Fe, Co, Ni, Cu) clusters using density functional theory calculations and the climbing image nudged elastic band algorithm. From the potential energy profiles, we found that CO 2 is prone to dissociate into adsorbed CO via the redox route with lower activation energies, E a 's, than the carboxyl route on all studied TM 13 systems. Our results suggested that the smaller activation barrier found on the Co 13 cluster is due to the stronger adsorption exhibited for both CO 2 and O. By increasing the d-state occupation (from Fe to Cu), the E a differences between CO 2 dissociation and COOH formation decrease. We associated this behavior with a decrease in the (CO 2 + H) adsorption energy from Fe 13 to Cu 13 that facilitates the COO−H bond formation and H−TM bond cleavage, i.e., favoring the carboxyl route. Also, our analyses indicate that the adsorption energies of the CO 2 and trans-COOH species are the best descriptors for the C−O bond dissociation via the redox and carboxyl routes, respectively.

Nature of Catalytic Behavior of Cobalt Oxides for CO2 Hydrogenation

“…The C–O bond cleavage is usually related to the C–O bond length, the longer C–O bond length is more prone to break the C–O bond. 34 Interestingly, the adsorption energies of *O atoms ( E (*O)) have a good linear relation with the C–O bond length ( Figure 2 d), implying that E (*O) may be used to reveal the nature of C–O bond scission. To further quantify the chemical bond strength, we calculated the integrated crystal orbital Hamilton population (ICOHP) of the C–O bond, where the smaller value of -ICOHP means the weaker C–O bond strength.…”

“…The C–O bond cleavage is usually related to the C–O bond length, the longer C–O bond length is more prone to break the C–O bond . Interestingly, the adsorption energies of *O atoms ( E (*O)) have a good linear relation with the C–O bond length (Figure d), implying that E (*O) may be used to reveal the nature of C–O bond scission.…”

Mechanisms of Complete Dissociation of CO2 on Iron Clusters

“…It was found in another combined work that even diatomic hydride anions CoH − and NiH − are capable to reduce CO 2 . Da Silva et al [22,23] . investigated CO 2 reduction catalyzed by 3 d ‐metal clusters Fe 13 , Co 13, Ni 13 , and Cu 13.…”

“…Since the structure and magnetic properties of iron clusters were the subject of numerous experimental and theoretical studies, [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] we have used in this work the commonly accepted groundstate geometrical structures and spin multiplicities for the host clusters. As representatives, we selected three iron clusters; namely, the smallest iron cluster Fe 2 , a Fe 4 cluster which was found [23] to be capable of splitting the N 2 dimer, and a Fe 16 cluster which was recently studied with respect to its interactions with nitrogen atoms and an N 2 dimer. [45] Using gradient based methods, we found pathways for the complete CO 2 dissociation to C + O + O on each Fe n cluster for n = 2, 4, and 16.…”

“…It was found in another combined work that even diatomic hydride anions CoH À and NiH À are capable to reduce CO 2 . Da Silva et al [22,23] investigated CO 2 reduction catalyzed by 3d-metal clusters Fe 13 , Co 13, Ni 13 , and Cu 13. Activation of CO 2 by atoms, clusters and molecules was recently reviewed by Wang et al [24] whereas recent advances in CO 2 reduction by atomically precise nanoclusters were reviewed by Quin at el.…”